Electric annealing furnace



April 3, 1951 J. J. STORDY ELECTRIC ANNEIALING FURNACE 2 Sheets-Sheet 1 Filed Nov. 4, 1949 INVENTOR JOHN J- STORDY ATTORNEY April 3, 1951 J. J. STORDY ELECTRIC ANNEAEING FURNACE 2 Sheets-Sheet 2 Filed NOV. 4, 1949 INVENTOR JOHN. J. STORDY ATTORNEY Patented Apr. 3, 1951 UNlTED STATES PATENT OFFICE.

-ELE CTRIG' ANNEALING FURNACE John I. Study, Albrighton, Wolverhampton, 'Englainm'assignor to Stordy Engineering Limited, Wolverhampton, England Application November 4, 1949, Serial No. 125,413 In Great Britain November 16, 1948 1"Claim. 1

This invention relates "to furnaces for the continuous annealing of metal sheets, more especially aluminium and other metal sheets which are annealed at relatively low temperatures.

In the annealing of aluminium sheets the latter are carried through a relatively long furnace and the heating is effected by electric "heaters usually secured to the under surface'of the roof of the furnace and shielded. The process has, however, disadvantages in that the heater elements are not'easily replaceable and 'even distribution of heat in'the entireworkin'g chamber is not obtained because there is considerable radiation from the elements even though a degree of air circulation is adopted.

The present invention has for object to overcome these disadvantags.

According to the invention, the annealing furnace has associated therewith one or more heating chambers which or each of which contains a battery of electric heaters, and air is blown through'said heating chamber or chambers into the furnace, where it is caused to flow over the metal sheets, and is'returned from'thence, by way of a fan or fans, to the heating chamber or chambers forreheating and recirculation. The heating chamber or chambers, or the battery or batteries of heating elements contained therein, is or are readily removable so that should an heater element fail, the respective heater battery or chamber can beuu'ickly removed and replaced by another battery or chamber and the faulty heater repaired.

Preferably there are two heating chambers located one over each end of 'the'furnace andeach containing a readily removable heater battery and air is supplied to each heating chamber by a separate fan drawing air from the middlezone of the furnace, the two fans being located between the heating chambersand each near the chamber which it supplies. The air flow through the furnace is preferably controlled and directed by an arrangement of distributive duct work and/or baflles, and in this connection provision may be made whereby a proportion of the air flow may be by-passed so as to afford a degree of control of turbulence.

Th invention will now be more fully described with reference to the embodiment shown, by way of example, in the accompanying drawings, in which- Figs. 1 and la taken together show a side elevational view of one preferred embodiment of the present invention.

Figs. 2 and 2a taken together show a plan view of the furnace shown in Figs. 1 and 1a.

Fig. 3 is an end view of the furnace shown in Figs. 1 andla.

Fig. 4 is a section taken on the line A, A of Fig. 1.

Referring to the drawings, the furnace comprises a steel plate casing I supported a short distance aboveground level upon transverse girder members 2 which interconnect vertical channel iron frame members 3 space'd'apartthroughoutthelength of the furnace and to which the steel plate side Walls of the casing are Welded'or otherwise secured. The-furnace casing I is lined with insulating and refractory brickwork 4 which defines a relatively long working chamber 5 extending from end to end of the furnace.

The'aluminium or other sheets to be annealed are travelled through-the furnace chamber ion the upper stretch of an endless conveyor 6 comprising a series of wires arranged side by side between grooved endrollers or multiple pulleys "I, 8, The direction of travel of the upper stretch of the conveyor '6 is from left to right, as seen in Figs. 1 and 2, and the roller or pulley 8 at the delivery or right-hand end is the driver, being itself driven by an endless chain 9 from an electric motor I0, whilst the roller or pulley I at the receiving end is an idler. The upper stretch of the conveyor 6 is supported at spaced points in its length by transverse rolls II mounted for rotation in bearing brackets fixed to the vertical frame members 3, whilst the return stretch of the conveyor 6 passes below the furnace casing I and its supporting girders'2 and is also supported at spaced points in its length by rolls I2 which are carried by bearing brackets fixed to the bottom of the casing I. a

The sheets are fed to the furnace conveyor by an endless feeding conveyor I3 of similar 'construction and the wires of which; pass between those of the conveyor 6 where the two conveyors overlap at the receiving end of the furnace. In this connection the roller or multiple pulley M at the delivery end of the feeding conveyor I3 is located to the right of or beyond the idler roller or pulley l of the conveyor 6 and is driven by an endless chain I5, bevel gearing I6, longitudinal side shaft I1, and bevel gearing I8 from the electric motor I0. As the sheets are fed to the furnace they are travelled between side guides which correctly locate the sheets centrally upon the conveyor 6 for passage through the furnace chamber 5 At the delivery end of the furnace the sheets are transferred directly from the conveyor 6 to a third conveyor I9 which travels them through a relatively long cooling chamber 26 through which a supply of cool air is maintained by a fan and distributive ducting mounted over the conveyor [9.

The ends of the furnace chamber 5 are fitted with vertically sliding doors 2| which can be operated in their guides 22 by suspension chains 23 and. hand winding gear 24, the arrangement being such that the doors can be lowered to a closed position, as shown in Fig. 3, so that the sheets supported on the conveyor 6 can just pass beneath their lower edges, or can be raised-to give free access to the interior of the furnace.

At each end of the furnace there is a large rectangular inlet duct 25 extending through the refractory lining of the top, and surmounting each duct 25 is a heating chamber of corresponding rectangular form afforded by the refractory lining of a heater casing 26, and said chamber contains a battery of electric heating elements (not shown) which are distributed substantially over the whole cross sectional area of said chamber- Each heater casing 29 is fitted with a removable cover 21 which has a refractory lining defining a supply duct 28 connecting the pressure side of a fan 29 to the heating chamber. There are two fans 29 associated one with each of the two heating chambers, thetwo fans 29 being located between the heating chambers on the top of thefurnace and each near to the chamber which it supplies, and each fan 29 draws air from the upper region of the furnace chamber 5 through a separate suction duct 30 which is located approximately mid-way between the adjacent end of the furnace and the middle zone of the latter. Each fan 29 is driven by a separate electric motor 3 1.

Air blown by the fans 29 through the ducts 28 and heating chambers passes over the heater batteries thereinand through the inlet ducts 25 on to the metal sheets. The hot air is then caused to flow over the sheets and along the lower region of the furnace chamber 5 toward the middle zone thereof by plate baffles 32 which are of zig-zag form and extend fully across the chamber 5 and from the air inlets 25 to the mid zone. At or near the mid zone of the furnace chamber, the meeting flows of hot air from the two heating chambers then come under the suction of the fans 29 which draw off the air from the upper regions of the chamber 5, above the bafiies 32, and pass it to the heating chambers for re-heating.

In the event of an element or elements in either of the heater batteries failing, the defective battery can be readily lifted out, upon removing the cover 21, and replaced by a fresh battery of heating elements.

In a modification the or each heating chamber, complete with its battery of heating elements, can be removed and replaced by another heating chamber containing'a heater battery,

Instead of providing for the heater battery being lifted out of its heating chamber, provision may be made for removing the battery laterally therefrom.

The heater batteries at both ends preferably are each subdivided into lowerratings so that, by means of selective switching on the control panel (not shown), the heat input to the zones of the furnace can be predetermined and thereafter held by automatic control without necessitating adjustment of the air supply. An advantage of this is that the. effect of cold work entering the furnace can be automatically compensated for by providing for greater heat input from the battery at the ingoing end of the furnace.

Having fullydescribed my invention, what I claim and desire to secure by Letters Patent is:

v A furnace for the continuous annealing of metal objects, comprising in combination a furnace chamber, means for conveying the objects through said chamber, two heating chambers one over each end of the furnace and each having an inlet to the furnace chamber at the respective end, a readily removable battery of electric heating elements, each of which can be selectively switched on, in each of the two heating chambers, two fans associated one with each heating chamber and connected for blowing air therethrough and through the respective inlet into the respective end of the furnace chamber and for drawing air from the mid zone of the furnace so that said air will be reheated and recirculated, and baffles extending across thefurnace chamber and from the respective inlets to the mid zone so as to direct the hot air flows from the ends of the fur nace chamber and over the objects to the mid zone from which the air is drawn oif by the fans.

JOHN J. STORDY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,294,756 Benjamin Feb. 18, 1919 1,525,725 Dressler Feb. 10, 1925 1,931,927 Klees Oct. 24, 1933 2,113,522 7 Walker Apr. 5, 1938 2,115,586 McFarland Apr. 26, 1938 2,130,756 Malam Sept. 20, 1938 2,290,551 Gier July 21, 1942 2,296,806 Buckholdt Sept. 22, 1942 2,391,970 Holleran et a1 Jan. 1, 1946 2,441,500 Miess May 11, 1948 OTHER REFERENCES Industrial and Engineering Chemistry, June, 1948; volume 40, No. 6, pages 1039-1044. 

